In conventional speakers, there is a speaker that uses ultrasonic waves as carrier waves called a parametric speaker (for example, refer to Patent Document 1). In the speaker described in Patent Document 1, a plurality of piezoelectric vibrators each having a piezoelectric element are arranged in a matrix, and modulated ultrasonic waves (carrier waves) are emitted into the air from the respective piezoelectric vibrators. With these emitted ultrasonic waves subjected to a non-linear phenomenon of air, a demodulated audible sound is generated.